Fine focusing table

ABSTRACT

A fine-focusing stage for microscopes, with an object carrier (1) , a holder (2) for the object carrier (1) and a positioning mechanism (3) adjusting the support in its horizontal position. In order to achieve parallel vertical displacement of the object carrier (1) using simple methods of construction the invention is so designed that the holder (2) comprises a mounting portion (4) preferably for mounting on an object stage or on the microscope and a connecting portion (5) with the object carrier, and articulated parallel arms (8,9) through bending elements (6,7) extend between the mounting portion (4) and the connecting portion (5).

BACKGROUND OF THE INVENTION

The invention concerns a fine-focusing stage for microscopes, with anobject carrier, a holder for the object carrier, and a positioning meanswhich changes the vertical Z-axis position of the object carrier.

In ordinary microscopy, the object is focused by the microscope focusingdrive. Positioning accuracy attainable with motors--usually DCmotors--is about ±50 nm. Such values are inadequate, by a factor of morethan two, so such focusing is not useful. External stepping motors arealso often attached to the fine focusing drive of the microscope. Bygearing down sufficiently, fine step divisions can be achieved; but theinternal or external gearing needed very substantially limitsmovability.

Gear-free direct drives are already known in practice. Positioningaccuracies in the nanometer range are attained with such direct drives.However, the range of motion is limited to a few hundred micrometers.There is the further problem here that such a direct drive, forinstance, moves only one objective, which then projects far past theother objectives.

Z-stages which can be moved by piezoactive elements are also known inpractice. However, the range of movement of such Z-stages is limited bythe piezoelements. Piezo assemblies are also expensive because of theexternal measurement system required and because of the high-voltagecontrol systems also needed.

Almost any desired Z scan rates can be attained with piezo control,including constant rapid and also very slot Z scan rates, such as 1000μm per second to 0.01 μm per second. Speed tolerances less than ±0.5%can, in any case, be attained with geared motors only with extremedifficulty.

Now if a fine-adjustment stage is to be used in a conventionalmicroscope, its design requires extreme flatness, with heights of about5 mm desirable. Also, there must be a hole in the center of the stagefor the light to pass through.

Z-stages with galvanometrically driven tilt plates have also been knownin practice for some years. The disadvantage of such a system, though,is that the object is necessarily moved laterally as it is lifted, withlarge lift movements. If the object being observed is in the plane ofthe pivot of the tilt plate the error due to the lateral movement isnegligibly small. For objects, or areas of objects, more distant fromthe plane of pivoting, though, this error becomes unacceptably large asthe distance increases.

SUMMARY OF THE INVENTION

The invention is based on the objective of designing and developing afine-focusing stage for microscopes of the type discussed here such thatno error occurs even with large vertical movement of the object carrier.Furthermore, the fine-focusing stage should be simple in design and itshould be possible to make it as thin as possible.

The fine-focusing stage according to the invention attains the objectiveabove by being designed so that the holder comprises a mounting portion,preferably fastened to the microscope stage or to the microscope, and aconnecting portion to the object carrier, and that hinged parallel armsextend between the mounting portion and the connecting portion throughbending elements.

It is known according to the invention that adjustment errors whichoccur in the usual Z-stages can be avoided if the object carrier has aparallel lift characteristic. Therefore the holder has a mountingportion which can be attached rigidly to the holder. In the actual case,the mounting portion fastens either to the microscope stage or to themicroscope itself. The holder also has a connecting portion to theobject carrier, so that the object carrier is effectively connected tothe mounting portion. Parallel arms hinged at bending elements extendbetween the mounting portion and the connecting portion, so that thebending elements occur between the mounting portion and the parallelarms, and also between the parallel arms or the connecting portion andthe microscope stage.

The characteristic claimed here always assures that the horizontalposition of the microscope stage does not change as it moved upward ordownward, that is, that the object carrier has a parallel liftcharacteristic. It is of very special importance in this respect thatthe mounting portion of the holder is in a fixed position and that theparallel arms are a connection between the horizontal object carrier andthe mounting portion, where the bending elements make it possible forthe parallel arms to bend with respect to the object carrier and withrespect to the mounting portion. Finally, the tilt error of the objectcarrier in the usual Z-stages is compensated by the hinging to theobject carrier by means of parallel arms and through defined bendingelements.

BRIEF DESCRIPTION OF THE DRAWINGS

Now there are various ways advantageously to embody and develop theteaching of this invention. One must refer to the following explanationof one embodiment of the invention, using the drawing. In combinationwith explaining the preferred example embodiment of the invention, thegenerally preferred embodiments and developments of the teaching areexplained. The drawing shows:

FIG. 1: a schematic lateral view, sectional along the line I--I of FIG.2, showing an example embodiment of a fine-focusing stage according tothe invention; and

FIG. 2: the item of FIG. 1 in a plan view, with two alternativepositioning means shown.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 together show one example embodiment of a microscopefine-focusing stage. For simplicity, only the fine-focusing stage itselfis shown here. The fine-focusing stage comprises an object carrier 1, aholder 2 for the object carrier 1, and a positioning means 3 whichchanges the vertical Z-axis position of the object carrier 1.

According to the invention, holder 2 includes a mounting portion 4, usedpreferably for mounting to an object stage not shown here or to themicroscope--between the microscope and the objective lens. The holder 2also comprises a connection portion 5 to the object carrier 1, such thatparallel arms, 8, 9 extend between the mounting portion 4 and theconnecting portion 5 through bending elements 6, 7.

FIG. 2 shows particularly clearly that the object carrier 1 is designedas a rectangle, and is connected to the parallel arms 8, 9 through thebending element 7 and the connecting portion 5. The bending element 7extends parallel to the connecting edge 10 of object carrier 1.

FIG. 2 also shows that the holder 2 is designed in the form of a frame11 surrounding the object carrier 1. The frame 11 is also rectangular.The object carrier 1 is slightly separated from the surrounding frame11, with the connecting edge 10 or the connecting region 5 on the sideof object carrier 1 opposite the mounting portion 4. Furthermore, thebending element 6 runs between the mounting portion 4 and the parallelarms 8, 9, parallel to the internal edge 12 of frame 11 nearest mountingportion 4, such that the edge 12 is consequently parallel to theconnecting edge 10.

The fine-focusing stage shown in FIGS. 1 and 2 is further designed sothat two opposite frame legs 13, 14 are attached to the mounting portion4 and the connecting portion 5 through the bending elements 6, 7, and sothat the other two mutually opposite frame legs 15, 16 each comprise oneparallel arm 8, 9.

In the actual design, the object carrier and the holder 2 comprise twosuperimposed identical plates 18, 18, partially firmly connectedtogether, as can be seen particularly well from FIG. 1. These plates 17,18 have spaces 19 which pas through and form three edges of the objectcarrier 1. Furthermore, a smaller thickness giving separation isprovided in plates 17, 18 in the vicinity of the frame 11 on the sidesof plates 17, 18 which face each other, so that there is a space 20between the frame legs 13, 14, 15 and 16. Recesses 21 are also providedon the sides of plates 17, 18 which face each other. Those, finally,define the bending elements 6, 7, with the minimum remaining wallthickness to achieve bending.

FIG. 1 also shows that the holder 2 and the object carrier 1 have thesame thickness, a total thickness of about 6 mm being provided here.

According to the presentation in FIG. 2, the object carrier 1 has apassage 22 for the light beam in about its middle.

Two alternative arrangements for the positioning means 3 are shown inFIG. 2 of the selected example embodiment. As shown in the drawing ofFIG. 1, the positioning means 3 attaches directly to the object carrier,on the side opposite the connecting portion 5. As shown by the drawingin FIG. 2, the positioning means either attaches directly to the objectcarrier 1 or to the frame leg 14 of the mounting portion 4. Whatever theactual arrangement, a cord 24 acts between the object carrier 1 or theframe 11 and the galvanometer drive 23 for the positioning means 3,using a galvanometer drive 23.

With respect to an actual design of object carrier 1, it is advantageousfor it to be designed as a rectangle and for the object carrier to beconnected, in the vicinity of its edges, specifically in the vicinity ofthe connecting edges 10, with the parallel arms 8, 9 through bendingelement 7 and connecting portion 5. A rectangular design of the objectcarrier offers a very significant advantage both with respect to theproduction engineering and with respect to a back-and-forth scan ofobjects.

The bending element 7 for object carrier 1 can be parallel to theconnecting edge 10 of the object carrier. Finally, this bending element7 is parallel to the opposing open edge of the object carrier, so thatthis bending element acts as a hinge for the object carrier.

It is also advantageous, from the viewpoint of production engineering,for the holder 2 to be made in the form of a frame 11 surrounding theobject carrier 1. Frame 11 can also be made rectangular, correspondingto the shape of object carrier 1. The object carrier 1 could be at leastslightly separated from the surrounding frame, so that the connectingedge 10 or the connection portion 5 of the object carrier lies on theside of the mounting portion 4 of the holder 2 opposite to the objectcarrier. In any case, the object carrier in the form under discussionhere is quasi-integrated into the frame 11 and can be forced out of theplane of the frame, at which time the parallel arms 8, 9 are allowed topivot at the bending elements.

The bending element 6 between the mounting portion 4 and the parallelarms 8, 9 could run parallel to the edge of the frame toward themounting portion. That would assure that all the edges of the objectcarrier 1 run parallel to the edges of the holder 2 or of the frame 11.Then the bending elements would also be directed parallel to the edgesof the frame and of the object carrier.

In a further advantageous manner, two opposite legs 13, 14 of the frame11 are connected through the bending elements 6 and 7 to the mountingportion 4 and the connecting portion 5, respectively, so that the othertwo opposing legs 15, 16 of the frame each comprise two parallel arms 8,9. Finally, the frame 11 comprises a total of four frame legs. Twoopposite frame legs 13, 14 are connected to the mounting portion 4 onone hand and to the connecting portion 5 on the other hand. The othertwo frame legs 15, 16, which are also opposite each other, make up theparallel arms 8, 9, so that each parallel arm--on each side--is madedouble, and so that the parallel arms are parallel to each other at adistance shift with respect to each other during the lifting movement ofthe object carrier 1, corresponding to the excursion, or correspondingto the lift of the object carrier. That, again, is due to the thicknessof the frame 11 and the design of the bending elements.

In a specific case, the object carrier 1 and the holder 2 could be madeof two identical plates, one above the other, firmly connected to eachother. The plates have cutouts or passages 19 going through the platesto form three adjacent edges of the object carrier. In the vicinity ofthe frame and in the vicinity of the bending elements they have,likewise, thin cutouts of reduced thickness or recesses 21 on thematching sides of the plates, providing separation.

The lesser thickness in the vicinity of the frame leads to a mutualseparation of the frame legs for the individual plates, so that relativemotion or shifting is possible between the parts of the frame legs incase of a lifting movement of the object carrier. The cutouts orrecesses in the vicinity of the bending elements define the endingelements and are designed in a further advantageous manner such that theremaining thickness of the material--toward the surfaces of theindividual plates--assures long term resistance of the plates tobending.

In any case, the design described above leads to the plates being firmlyconnected together only in the vicinity of the object carrier 1 and themounting portion 4. It also results in the reduced thickness in theframe area, on one hand, and the cutouts or recesses in the vicinity ofthe bending elements, on the other hand, thereby separating the plates.In case of deflection of the object carrier or of the frame area orconnecting portion turned toward or opposite to the mounting portion,parallel lifting of the object carrier is possible.

According to the actual embodiment above, it is possible for the holder2 and the object carrier 1 to have the same thickness, so that a flatform of the fine-focusing stage can be accomplished. The thickness ofthe holder 2 and the object carrier 1 can, without further discussion,be in the range from less than 5 mm to about 10 mm.

It is also possible to provide a passage 22 in about the center of theobject carrier 1 for the light beam to pass, as in use as a stage itransmitted light microscopy, or for use directly on the objective lens.The size of this passage is based on the requirements of the particularcase.

The object carrier 1 and the holder 2 can be made of stainless steel oraluminum, for example. In both cases, simple metal-cutting work ispossible. It would also be conceivable to produce the individual partsof the fine-focusing stage--the two plates making up the fine-focusingstage--by injection molding. The cutouts and recesses could be providedby the mold. Otherwise, a milling process and subsequent assembly of theindividual plates would be required.

With respect to the positioning means 3 mentioned initially, it would beadvantageous, in view of a particular simple design, for the positioningmeans to attach directly to the object carrier 1, preferably on the openside opposite the connecting portion 5. Finally, the object carrier herecould be forced upward or downward, accomplishing a parallel lift of theobject carrier. It would, similarly, be conceivable to attach thepositioning means on the frame leg 14 for the connection portion 5, sothat an appropriate upward or downward force would also give a parallellift for the object carrier.

Ordinary means are used as drives for the positioning means 3. A singleor multiple stage drive can be provided advantageously for the coarseand fine movement of the object carrier 1. For very specially accurateand reproducible adjustment of the focus, one could provide agalvanometer drive 23 with a cord 24 running between the frame 11 or theobject carrier 1 and the galvanometer drive. The object carrier and/orthe frame could be pulled or moved directly upward or downward,depending on the arrangement of the galvanometer drive, so as toaccomplish a parallel lift of the object carrier.

With respect to potential applications of the fine-focusing stage, itmust be noted particularly at this point that the fine-focusing stagecan be incorporated as an intermediate unit between the microscope andthe objective lens or the objective nosepiece. It is also possible tofasten the fine-focusing stage with its holder to the microscope objectstage, so that the focus position of the object can be adjustedextremely finely. In any case, the fine-focusing stage according to theinvention can provide rapid and precise adjustment of the focus inconfocal microscopy, corresponding to a definite requirement forconfocal microscopy.

List of reference numbers

1 Object carrier

2 Holder for the object carrier

3 Positioning means

4 Mounting portion

5 Connecting portion

6 Bending element

7 Bending element

8 Parallel arm

9 Parallel arm

10 Connecting edge

11 Frame

12 Edge of the frame

13 Frame leg

14 Frame leg

15 Frame leg

16 Frame leg

17 Plate

18 Plate

19 Cutout

20 Space

21 Cutout

22 Passage

23 Galvanometer drive

24 Cord

What is claimed is:
 1. A fine-focusing stage for a microscopecomprising:a holder including a mounting portion adapted for attachmentto a microscope, a connecting portion opposite said mounting portion,and a pair of parallel arms extending between said mounting portion andsaid connecting portion, said pair of parallel arms being connected tosaid mounting portion by a bending element for permitting bendingbetween said pair of parallel arms and said mounting portion; an objectcarrier connected to said connecting portion of said holder by a secondbending element for permitting bending between said object carrier andsaid connecting portion, said object carrier having a free edge oppositesaid second bending element extending parallel to bending lines definedby said first and second bending elements; and positioning means formoving said object carrier in along a vertical Z-axis.
 2. Thefine-focusing stage according to claim 1, wherein object carrier is inthe shape of a rectangle.
 3. The fine-focusing stage according to claim2, wherein said holder is a frame surrounding said object carrier. 4.The fine-focusing stage according to claim 3, wherein said frame is inthe shape of a rectangle.
 5. The fine-focusing stage according to claim4, wherein said frame includes an internal edge nearest said mountingportion, and said bending lines are parallel to said internal edge. 6.The fine-focusing stage according to claim 4, wherein said frameincludes two parallel frame legs, each of said frame legs having a pairof said parallel arms extending between said mounting portion and saidconnecting portion.
 7. The fine-focusing stage according to claim 4,wherein said object carrier and said holder are made of two identicalsuperimposed plates fixed together at said mounting portion.
 8. Thefine-focusing stage according to claim 7, wherein cut-out gaps areprovided through said plates to separate said object carrier from saidholder along three adjacent edges of said object carrier, and saidplates are of reduced thickness on facing sides of said plates in thevicinity of said frame to provide separation between said pair ofparallel arms.
 9. The fine-focusing stage according to claim 7, whereinsaid first and second bending elements are defined by cut-out channelsreducing the thickness of said plates.
 10. The fine-focusing stageaccording to claim 1, wherein said holder is a frame surrounding saidobject carrier.
 11. The fine-focusing stage according to claim 10,wherein said free edge of said object carrier and said mounting portionare on a same side of said stage.
 12. The fine-focusing stage accordingto claim 10, wherein said positioning means includes a galvanometerdrive having a cord acting between said frame and said galvanometerdrive.
 13. The fine-focusing stage according to claim 1, wherein saidobject carrier and said holder are made of two identical superimposedplates fixed together at said mounting portion.
 14. The fine-focusingstage according to claim 1, wherein said holder and said object carrierhave a same thickness.
 15. The fine-focusing stage according to claim14, wherein said thickness is in a range from 5 mm to 10 mm.
 16. Thefine-focusing stage according to claim 1, wherein said object carrierincludes a centrally located passage therethrough for transmittinglight.
 17. The fine-focusing stage according to claim 1, wherein saidholder and said object carrier are made of stainless steel.
 18. Thefine-focusing stage according to claim 1, wherein said holder and saidobject carrier are made of aluminum.
 19. The fine-focusing stageaccording to claim 1, wherein said positioning means is attached to saidobject carrier.
 20. The fine-focusing stage according to claim 19,wherein said positioning means is attached to said object carrier at alocation remotely of said second bending element.
 21. The fine-focusingstage according to claim 1, wherein said positioning means is attachedto said connecting portion.
 22. The fine-focusing stage according toclaim 1, wherein said mounting portion is adapted for attachment to anobject stage of a microscope.
 23. The fine-focusing stage according toclaim 1, wherein said positioning means includes a drive having at leasttwo stages for respective coarse and fine movement of said objectcarrier.
 24. The fine-focusing stage according to claim 1, wherein saidpositioning means includes a galvanometer drive having a cord actingbetween said object carrier and said galvanometer drive.